Converting an AWA RT85 LOW BAND Transceiver

to 6 Metres

by Roger Baker VK3BKR and Mark Detering VK3TLW

Notes apply to the RT85. NOT the RT85A,B, or C

REPROGRAMMING THE EPROM

Either, we can programme your EPROM for you with OUR channels, or, you are on your own.

The RX VCO.

Add lOp to C709.

TX VCO.

Add lOp to C137

The EXCITER

Remove original L114 and keep (for use in PA Board); replace with 7.5 turns O.5mm wire

The RECEIVER

Add lOp to C202
Add 22p to C205.
Add 22p to C208.
Add 22p to C212.
Add 4p7 to C220.

P.A. BOARD.

Add 22p to C512.
Remove original L501 and keep; replace with original L114 (fom the Exiter board)
Remove original L503 and keep; replace with original L501.
Remove original L507 and replace with original L503.
Remove original L513 and keep, replace with 2.5 turns 1.25mm wire.
Remove original L512 and replace with original L513.

RX VCO

The RX VCO will probably be out of lock when the radio is first powered up. The display will show "95" and the speaker will beep.
Connect a multimeter to TP701 and adjust for approximately 4.7 volts. It should now be possible to change channels up and down.
Set the radio to Channel 18 (53.975MHz highest Rx), and adjust L701 for 4.70 volts.
Set the radio to channel 37 (52.500MHz lowest Rx) and check that the voltage is NOT less than 1.6 volts.

TX VCO

Set the radio to channel 36 (53.975 MHz highest Tx) and connect a multimeter to TPl0l. Operate the PTT and adjust L107 for 4.70 volts.
Set the radio to channel 37 (52.500 MHz lowest Tx) and operate the PTT and check that the voltage is NOT less than 1.6 volts

LO Injection

Connect a multimeter to pin 4 on CM202 on the Receiver board. Adjust L209 and L210 for maximum indication on the meter (about 0.5 volts).

RX Tuning

Using a suitable signal source, adjust the RX front end slugs for best bandpass

TX Tuning

Connect multimeter to TP101 and adjust L107 for 3.5v on a centre channel
Adjust CV102 for max RF output
Set RV502 to fully clockwise position
Adjust CV501, 502 AND 503 for Maximum Power output
Re-adjust RV502 for approx 25W (or slightly less than whatever power is attained in the previous step as this enables your PA protection circuitry).
Set Deviation at 4.5khz using RV501
L101 and L102 may be adjusted slightly to give deviation symmetry

These mods should result in the receiver having a sensitivity of approx 0.25uV and a Tx power of at least 25Watts

Our Channels are

Ch	Rpt Rx	Ch	Rpt Rx
1	53.550	19	52.550
2	53.575	20	52.575
3	53.600	21	52.600
4	53.625	22	52.625
5	53.650	23	52.650
6	53.675	24	52.675
7	53.700	25	52.700
8	53.725	26	52.725
9	53.750	27	52.750
10	53.775	28	52.775
11	53.800	29	52.800
12	53.825	30	52.825
13	53.850	31	52.850
14	53.875	32	52.875
15	53.900	33	52.900
16	53.925	34	52.925
17	53.950	35	52.950
18	53.975	36	52.975

Ch	Simplex	Ch	Simplex
37	52.500	55	53.400
38	52.525	56	53.425
39	53.000	57	53.450
40	53.025	58	53.475
41	53.050	59	53.500
42	53.075	60	53.525
43	53.100
44	53.125
45	53.150
46	53.175
47	53.200
48	53.225
49	53.250
50	53.275
51	53.300
52	53.325
53	53.350
54	53.375

Roger Baker VK3BKR and Mark Detering VK3TLW